Optical fiber scanning apparatus and endoscope

ABSTRACT

An optical fiber scanning apparatus includes an optical fiber a fixed end of which is fixed and a free end for emitting illumination light of which vibrates in a first direction and a second direction, a ferrule which includes a through hole including an opening on a distal end surface and fixes the optical fiber inserted through the through hole, a pair of first fixing members which sandwich and fix the optical fiber in the first direction, a pair of second fixing members which sandwich and fix the optical fiber in the second direction, and piezoelectric elements or a magnet configured to vibrate the optical fiber, in which a Young&#39;s modulus of the pair of first fixing members is smaller than a Young&#39;s modulus of the pair of second fixing members.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation application of PCT/JP2016/088693filed on Dec. 26, 2016, the entire contents of which are incorporatedherein by this reference.

BACKGROUND OF INVENTION 1. Field of the Invention

The present invention relates to an optical fiber scanning apparatusincluding an optical fiber a free end of which vibrates in a firstdirection and a second direction perpendicular to the first direction,and an endoscope including the optical fiber scanning apparatus in adistal end portion of an insertion section.

2. Description of the Related Art

An image pickup apparatus including an image pickup device such as a CCDor a CMOS image sensor simultaneously receives reflected light from asubject using many light receiving elements arranged in a matrix shape,to acquire an object image. In an endoscope which shoots a dark insideof a body, an image in a range illuminated with light from a lightsource is acquired.

On the other hand, an optical scanning type image pickup apparatussequentially receives, while scan-irradiating an object with a lightspot, reflected light from the object, to generate an object image basedon data representing the received light.

For example, the optical scanning type image pickup apparatus performsthe scanning irradiation with the light spot when an optical fiberscanning apparatus vibrates a free end of an optical fiber in acantilevered state which guides light from a light source to performtwo-dimensional scanning.

Examples of means for vibrating the optical fiber include apiezoelectric driving method for attaching a piezoelectric element to anoptical fiber and vibrating the piezoelectric element disclosed in U.S.Pat. No. 6,294,775 and an electromagnetic driving method for vibrating apermanent magnet attached to an optical fiber using an electromagneticcoil disclosed in Japanese Patent Application Laid-Open Publication No.2008-116922. If the optical fiber is vibrated, when the optical fiber isvibrated in the vicinity of a resonance frequency of the optical fiber,a large deflection (displacement or amplitude) of the optical fiber isobtained with small energy.

To cause the free end of the optical fiber to scan two-dimensionally,X-axis direction scanning and Y-axis direction scanning, perpendicularto the X-axis direction need to be independently controlled. However, ifboth the scannings have the same resonance frequency, even when the freeend of the optical fiber is scanning in the X-axis direction, forexample, the free end of the optical fiber also unintentionally scans inthe Y-axis direction. Thus, a distortion may occur in a scan trajectory.

Japanese Patent Application Laid-Open Publication No. 2014-44265discloses an optical scanning apparatus which includes an optical fiberhaving different resonance frequencies, respectively, in an X-axisdirection and a Y-axis direction and performs stable scanningirradiation.

SUMMARY OF THE INVENTION

An optical fiber scanning apparatus according to an aspect of thepresent invention includes an optical fiber a fixed end of which isfixed and a free end for emitting illumination light of which vibratesin a first direction and a second direction perpendicular to the firstdirection, a ferrule which includes a through hole including an openingon a distal end surface and fixes the fixed end of the optical fiberinserted through the through hole, a pair of first fixing members whichsandwich and fix the optical fiber in the first direction, a pair ofsecond fixing members which sandwich and fix the optical fiber in thesecond direction, and piezoelectric elements or a magnet configured tovibrate the optical fiber, in which a Young's modulus of the pair offirst fixing members is smaller than a Young's modulus of the pair ofsecond fixing members.

An endoscope according to another aspect of the invention includes anoptical fiber scanning apparatus in a distal end portion of an insertionsection, the optical fiber scanning apparatus including an optical fibera fixed end of which is fixed and a free end for emitting illuminationlight of which vibrates in a first direction and a second directionperpendicular to the first direction, a ferrule which includes a throughhole including an opening on a distal end surface and fixes the fixedend of the optical fiber inserted through the through hole, a pair offirst fixing members which sandwich and fix the optical fiber in thefirst direction, a pair of second fixing members which sandwich and fixthe optical fiber in the second direction, and piezoelectric elements ora magnet configured to vibrate the optical fiber, in which a Young'smodulus of the pair of first fixing members is smaller than a Young'smodulus of the pair of second fixing members.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram of an endoscope system including anoptical fiber endoscope according to a first embodiment;

FIG. 2 is a cross-sectional view of an optical fiber scanning apparatusaccording to the first embodiment;

FIG. 3 is a perspective view of a principal part of the optical fiberscanning apparatus according to the first embodiment;

FIG. 4 is a front view of the principal part of the optical fiberscanning apparatus according to the first embodiment;

FIG. 5 is a cross-sectional view along a V-V line illustrated in FIG. 4of the principal part of the optical fiber scanning apparatus accordingto the first embodiment;

FIG. 6 is a perspective view of a principal part of an optical fiberscanning apparatus according to a modification 1 to the firstembodiment;

FIG. 7 is a cross-sectional view along a line VII-VII illustrated inFIG. 6 of the principal part of the optical fiber scanning apparatusaccording to the modification 1 to the first embodiment;

FIG. 8 is a front view of a ferrule in a principal part of an opticalfiber scanning apparatus according to a modification 2 to the firstembodiment;

FIG. 9 is an exploded view of a principal part of an optical fiberscanning apparatus according to a modification 3 to the firstembodiment;

FIG. 10 is a front view of a principal part of an optical fiber scanningapparatus according to a modification 4 to the first embodiment; and

FIG. 11 is a perspective view of a principal part of an optical fiberscanning apparatus according to a second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

An embodiment of the present invention will be described below withreference to the drawings.

As illustrated in FIG. 1, an endoscope 9 including an optical fiberscanning apparatus 10, together with a light source unit 2, a detectionunit 3, a driving signal generation unit 4, a control unit 5, a displayunit 6, and an input unit 7, constitutes an endoscope system 1.

Note that in the following description, it should be noted that thedrawings based on each of embodiments are schematic, and a relationshipbetween a thickness and a width of each of sections, a ratio ofthicknesses of the sections, and the like respectively differ fromactual ones, and the sections which also differ in a dimensionalrelationship and a ratio among the drawings may be included.Illustration of some of components and assignment of reference numeralsmay be omitted.

The endoscope 9 includes an elongated insertion section 9A to beinserted into a living body, an operation section 9B, and a universalcable 9C. The insertion section 9A in the endoscope 9 includes a distalend portion 9A1, a bending portion 9A2, and a flexible tube portion 9A3.Note that the endoscope 9 according to the embodiment is a so-calledflexible endoscope, but the endoscope 9 may be a so-called rigidendoscope in which the insertion section 9A is rigid and may be used formedical and industrial purposes.

In the operation section 9B, a bending operation knob 9B2 for performinga bending operation for the bending portion 9A2 is turnably disposed. Aconnection section between the insertion section 9A and the operationsection 9B is a grasping section 9B1 to be grasped by a user.

An optical fiber 12 for illumination, an optical fiber 13 for lightreceiving, a signal line 14 configured to transmit a driving signal fromthe driving signal generation unit 4 to a driving section 25 (see FIG.2) including piezoelectric elements, and the like are inserted throughthe universal cable 9C and the insertion section 9A and are connected tothe optical fiber scanning apparatus 10 disposed in the distal endportion 9A1.

The light source unit 2 multiplexes respective light beams from threelaser light sources each configured to emit CW (consecutive oscillation)laser light in three primary colors, e.g., red, green, and blue, andemits the multiplexed light beams as white light. Examples of the laserlight source which can be used include a DPSS (diode pumped solid state)laser and a laser diode. Needless to say, a configuration of the lightsource unit 2 is not limited to this. Examples of the light source unit2 may include a light source unit using one laser light source and alight source unit using other plurality of light sources.

When a distal end portion as a cantilever of the optical fiber 12vibrates by the driving section 25, spot illumination light to beemitted by the optical fiber 12 is caused to scan two-dimensionally toilluminate an object to be observed, as described below. Reflected lightfrom the object to be observed illuminated with the illumination lightenters the detection unit 3 via the optical fiber 13 for detection. Thedetection unit 3 decomposes the reflected light into spectralcomponents, and converts the spectral components into an electric signalusing a photodiode. The control unit 5 synchronously controls the lightsource unit 2, the detection unit 3, and the driving signal generationunit 4 while processing the electric signal to be outputted by thedetection unit 3, to synthesize images and display a composite image onthe display unit 6. The user performs settings of the endoscope system1, such as a scanning speed and brightness of the displayed image, viathe input unit 7.

Note that the light source unit 2, the detection unit 3, the drivingsignal generation unit 4, and the control unit 5 may be accommodated inthe same housing, or may be respectively accommodated in differenthousings.

As illustrated in FIGS. 2 to 5, the optical fiber scanning apparatus 10includes a housing 11, optical fibers 12 and 13, a ferrule 20 as aholding section, the driving section 25 configured to vibrate theoptical fiber 12, and an illumination optical system 15.

The optical fiber 12 guides the light from the light source unit 2, andemits illumination light from a free end 12F1. The illumination opticalsystem 15 including a plurality of lenses 15A and 15B is configured toconverge the spot illumination light emitted from the optical fiber 12on a surface of the object to be observed. Note that the illuminationoptical system 15 is not limited to a two-element lens, but may includeone lens or three or more lenses.

The optical fiber 13 for detection may have a light-converging opticalsystem disposed at the distal end of the optical fiber 13. Note that theoptical fiber scanning apparatus 10 includes a plurality of opticalfibers 13 to obtain a sufficient amount of detected light.

The ferrule 20 composed of zirconia, for example, includes a throughhole H20 having an opening on a distal end surface 20SA. A material forthe ferrule 20 is not limited to ceramic such as zirconia if a rigidmaterial. The ferrule 20 may be composed of metal such as nickel orresin. An inner diameter of the through hole H20 is slightly larger thanan outer diameter of the optical fiber 12. For example, the innerdiameter of the through hole H20 is larger than 100% and not more than105% of the outer diameter of the optical fiber 12. A distal end portionof the optical fiber 12 inserted into the through hole H20 constitutes acantilever to which a fixed end 12F2 is fixed and which is held along acentral axis (optical axis) O in a long-axis direction (Z-axisdirection) of the housing 11.

The optical fiber 12 is a vibration section constituting a cantilever inwhich a distal end portion in a range from the fixed end 12F2 as astarting point to the free end 12F1 vibrates in a first direction(Y-axis direction) and a second direction (X-axis direction)perpendicular to the first direction. The first direction and the seconddirection are perpendicular to the optical axis direction (Z-axisdirection). Note that it goes without saying that the first directionmay be the X-axis direction and the second direction may be the Y-axisdirection.

The free end 12F1 of the optical fiber 12 moves in a predeterminedscanning pattern within an XY plane by a combination of the vibration inthe first direction and the vibration in the second direction.

Examples of a scanning method include spiral scanning, raster scanning,and Lissajous scanning depending on a combination of a vibration patternin the first direction (Y-axis scanning) and a vibration pattern in thesecond direction (X-axis scanning).

The spiral scanning is performed while spirally changing a diameter bycontinuously changing a displacement amount in the first direction and adisplacement amount in the second direction. The raster scanning isperformed by combining low-speed scanning in the first direction andhigh-speed scanning in the second direction performed during thescanning in the first direction, for example. The Lissajous scanning isperformed by combining vibration (scanning) in the first direction andvibration (scanning) in the second direction which differ in frequency.A difference between a driving signal frequency in the first directionand a driving signal frequency in the second direction is an integer.

In the optical fiber scanning apparatus 10, the driving section 25configured to vibrate the optical fiber 12 includes piezoelectricelements (piezoelectric ceramics) 25A to 25D respectively disposed onfour side surfaces 20SSA to 20SSD of the ferrule 20 as a prism-shapedrectangular parallelepiped. In other words, the piezoelectric elements25A and 25B configured to drive the optical fiber 12 in an up-and-downdirection (Y-axis direction) are respectively disposed on the facingside surfaces 20SSA and 20SSB, and the piezoelectric elements 25C and25D configured to drive the optical fiber 12 in a right-and-leftdirection (X-axis direction) are respectively disposed on the opposingside surfaces 20SSC and 20SSD.

Note that when a reference numeral denotes each of a plurality ofcomponents, one alphabet character at the end of the reference numeralis omitted. For example, each of the piezoelectric elements 25A to 25Dis referred to as a piezoelectric element 25.

The piezoelectric element (driving section) 25 expands and contractswhen an alternating current driving signal (driving voltage) having apredetermined frequency is applied to the piezoelectric element 25 viathe signal line 14. Accordingly, when a Y-axis driving signal is appliedto the piezoelectric elements 25A and 25B, the free end 12F1 of theoptical fiber 12 vibrates in the first direction (Y-axis direction).When an X-axis driving signal is applied to the piezoelectric elements25C and 25D, the free end 12F1 of the optical fiber 12 vibrates in thesecond direction (X-axis direction).

When the control unit 5 controls the driving signal generation unit 4, adriving signal for performing two-dimensional scanning in apredetermined pattern is inputted to the driving section 25. In otherwords, the X-axis driving signal and the Y-axis driving signal which arecontrolled such that an irradiation position of the spot illuminationlight to be irradiated onto the object to be observed draws a trajectorycorresponding to a predetermined scanning pattern are inputted to thedriving section 25.

To perform the two-dimensional scanning in the predetermined pattern,when the vibration in the X-axis direction and the vibration in theY-axis direction are independently controlled (scanned) at a resonancefrequency or a frequency in the vicinity of the resonance frequency inat least one of the axis directions, a driving efficiency is good.However, if the optical fiber 12 has the same resonance frequency FR inboth the X-axis direction and the Y-axis direction, even when thescanning is being performed in the X-axis direction, for example, thescanning is also unintentionally performed in the Y-axis direction.Thus, a distortion may occur in a scan trajectory.

The resonance frequency FR of the optical fiber 12 is inverselyproportional to a square root of a length (vibration length) L of avibration section from the fixed end 12F2 to the free end 12F1 inprimary resonance. In other words, the smaller the vibration length Lis, the higher the resonance frequency FR becomes. In the optical fiber12, although the vibration length in the X-axis direction and thevibration length in the Y-axis direction are the same, effectivevibration lengths differ from each other. Thus, a resonance frequency atthe time when the optical fiber 12 vibrates in the X-axis direction anda resonance frequency at the time when the optical fiber 12 vibrates inthe Y-axis direction differ from each other.

In other words, in the optical fiber scanning apparatus 10, the opticalfiber 12 is fixed with the fixed end 12F2 sandwiched between the pair offirst fixing members 30A and 30B composed of solder in the firstdirection (Y-axis direction) and is fixed with the fixed end 12F2sandwiched between the pair of second fixing members 30C and 30Dcomposed of nickel in the second direction (X-axis direction).

More specifically, four grooves T20A to T20D each having an opening on awall surface of the through hole H20 are respectively formed atpositions which are rotationally symmetric around the optical axis O onthe distal end surface 20SA of the ferrule 20. The groove T20A and thegroove T20B are arranged to face each other on opposite sides of thethrough hole H20. Thus, the grooves T20A and T20B, together with thethrough hole H20, apparently constitute a continuous single groove.Similarly, the grooves T20C and T20D, together with the through holeH20, constitute a continuous single groove. A long-axis direction of thegrooves T20A and T20B is the first direction (Y-axis direction), along-axis direction of the grooves T20C and T20D is the second direction(X-axis direction), and a depth direction of the grooves 20A to 20D isthe optical axis direction (Z-axis direction).

Solder composing the first fixing members 30A and 30B is embedded in thepair of grooves T20A and T20B facing each other, and nickel composingthe second fixing members 30C and 30D is embedded in the pair of groovesT20C and T20D facing each other.

Note that the groove T20 may be embedded with the fixing member 30 onlyat least in the vicinity of the optical fiber 12 (the through hole H20),and the groove T20 needs not be filled with the fixing member 30 overits entire length. For example, the groove T20 may not be filled withthe fixing member 30 in the vicinity of the side surface 20SS of theferrule 20.

Solder composing the first fixing members 30A and 30B has a Young'smodulus Y1 of 42 GPa, and nickel composing the second fixing members 30Cand 30D has a Young's modulus Y2 of 207 GP.

Accordingly, a fixed state of the fixed end 12F2 differs, and theeffective vibration length in the X-axis direction and the effectivevibration length in the Y-axis direction differ from each other. Theeffective vibration length in the first direction in which the fixed end12F2 is fixed by the first fixing members 30A and 30B is larger than theeffective vibration length in the second direction in which the fixedend 12F2 is fixed by the second fixing members 30C and 30D having alarger Young's modulus.

Accordingly, a resonance frequency FR1 in the first direction of theoptical fiber 12 is 7824 Hz, and a resonance frequency FR2 in the seconddirection of the optical fiber 12 is 7890 Hz (ternary resonance in boththe first direction and the second direction). In other words, theresonance frequency FR1 in the first direction in which the fixed end12F2 is fixed by the first fixing members 30A and 30B is lower than theresonance frequency FR2 in the second direction in which the fixed end12F2 is fixed by the second fixing members 30C and 30D having a largerYoung's modulus than the Young's modulus of the first fixing members 30Aand 30B. A difference dFR between the resonance frequency FR1 and theresonance frequency FR2 is 66 Hz, and a ratio of the resonance frequencyFR1 to the resonance frequency FR2 is 0.84%.

In the optical fiber scanning apparatus 10, the resonance frequency FR1and the resonance frequency FR2 differ from each other. In the Lissajousscanning, an X-axis driving signal and a Y-axis driving signal can berespectively alternating current signals having substantially the samefrequencies as the resonance frequencies in the first direction and thesecond direction. Accordingly, the optical fiber scanning apparatus 10can perform stable scanning without a distortion occurring in the scantrajectory.

Note that the through hole H20 is arranged at a center of the ferrule20, i.e., an equal distance from the four side surfaces 20SSA to 20SSD.The optical fiber 12 matches a central axis of the driving section 25 bybeing only inserted into the through hole H20.

The optical fiber scanning apparatus 10 is easily manufactured becausethe optical fiber 12 needs not be processed. In the optical fiber 12,the fixed end 12F2 is fixed by the first fixing members 30A and 30B andthe second fixing members 30C and 30D. Thus, the vibration length is thesame in the X-axis direction and the Y-axis direction. Accordingly,control to causes the free end 12F2 of the optical fiber 12 to scantwo-dimensionally by the control unit 5 is easy. The endoscope 9including the optical fiber scanning apparatus 10 is easily controlledand manufactured because stable scanning can be performed.

In other words, although the optical fiber 12 has the same configurationin the directions (X-axis direction/Y-axis direction) perpendicular tothe optical axis in the optical fiber scanning apparatus 10, the Young'smodulus Y1 of the first fixing members 30A and 30B which sandwich andfix the optical fiber 12 in the distal end portion of the ferrule 20 issmaller than the Young's modulus Y2 of the second fixing members 30C and30D. Note that the Young's modulus Y1 may be larger than the Young'smodulus Y2. In other words, the first fixing members 30A and 30B and thesecond fixing members 30C and 30D may be respectively composed ofmaterials having different Young's moduli. Accordingly, in the opticalfiber scanning apparatus 10, the resonance frequency FR1 at the timewhen the optical fiber 12 vibrates in the first direction (Y-axisdirection) and the resonance frequency FR2 at the time when the opticalfiber 12 vibrates in the second direction (X-axis direction) differ fromeach other.

Although the difference dFR between the resonance frequencies requiredto perform stable scanning irradiation differs depending on aspecification of the optical fiber scanning apparatus 10, the resonancefrequencies preferably differ by 0.2% or more, and particularlypreferably differ by 0.5% or more, for example.

In the Lissajous scanning, an upper limit of the frequency of the Y-axisdriving signal is less than ((Y-axis resonance frequency FR1)+(0.5dFR)), and is preferably less than ((Y-axis resonance frequencyFR1)+(0.25 dFR)). A lower limit of the frequency of the Y-axis drivingsignal is preferably (0.9×(Y-axis resonance frequency FR1)) or more toefficiently drive the optical fiber 12.

Similarly, a lower limit of the frequency of the X-axis driving signalis more than ((X-axis resonance frequency FR2)−(0.5 dFR)), and ispreferably more than ((Y-axis resonance frequency FR2)−(0.25 dFR)). Anupper limit of the frequency of the X-axis driving signal is preferably(1.1×(X-axis resonance frequency FR2)) or less to efficiently drive theoptical fiber 12.

If a scanning method is the Lissajous scanning, the difference dFRbetween the resonance frequency FR1 in the first direction and theresonance frequency FR2 in the second direction of the optical fiber 12is preferably kN (Hz) (N and k are natural numbers) in an endoscopewhich shoots a movie with a frame rate of N (fps) with the reflectedlight from the object to be observed illuminated with the illuminationlight.

For example, one still image is shot in 1/30 seconds in a movie with aframe rate of 30 fps. In other words, both one cycle of scanning in thefirst direction and one cycle of scanning in the second direction are1/30 seconds. If the difference dFR between the resonance frequencies isa multiple of the frame rate N, e.g., 30 Hz, 60 Hz, or 90 Hz, a starttime and an end time of the one cycle of the scanning in the firstdirection and a start time and an end time of an N-th cycle of thescanning in the second direction match each other.

Note that the difference dFR between the resonance frequency FR1 and theresonance frequency FR2 is adjusted by a difference dY between theYoung's modulus Y1 of the first fixing members 30A and 30B and theYoung's modulus Y2 of the second fixing members 30C and 30D. In otherwords, the larger the difference between the Young's moduli is, thelarger the difference dFR between the resonance frequencies becomes.

In the optical fiber scanning apparatus 10, the first fixing members 30Aand 30B and the second fixing members 30C and 30D are composed of metal.However, resin such as epoxy resin (a Young's modulus: 3.5 GPa) orsilicone resin (a Young's modulus: 4 MPa) can also be used as a materialfor the fixing members.

In other words, at least one of the first fixing members 30A and 30B,and the second fixing members 30C and 30D may be composed of resin.Needless to say, at least one of the first fixing members 30A and 30B,and the second fixing members 30C and 30D may be composed of metal.

As the material for the fixing members, the first fixing members 30A and30B are preferably composed of metal having a Young's modulus anabsolute value of which is large, such as nickel, solder, gold (aYoung's modulus: 80 GPa), or copper (a Young's modulus: 130 GPa) and thesecond fixing members 30C and 30D are preferably composed of resinhaving a Young's modulus an absolute value of which is small because adifference between the Young's moduli is easily increased. Needless tosay, the second fixing members 30C and 30D may be composed of resin, andthe second fixing members 30C and 30D may be composed of metal.

Modifications to First Embodiment

Respective optical fiber scanning apparatuses according to modificationsto the first embodiment are similar to and have the same effect as theeffect of the optical fiber scanning apparatus 10. Thus, componentshaving the same functions are assigned the same reference numerals, anddescription of the components is omitted.

Modification 1 to First Embodiment

In an optical fiber scanning apparatus 10A according to a modification 1illustrated in FIGS. 6 and 7, corner portions respectively formedbetween a distal end surface 20SA and side surfaces 20SSA and 20SSB of aferrule 20A are chamfered.

The optical fiber scanning apparatus 10A uses the same fixing members30A to 30D as the fixing members used by the optical fiber scanningapparatus 10. In other words, respective corner portions, between thedistal end surface 20SA and the side surfaces 20SSA and 20SSB, ofgrooves T20A and T20B embedded with fixing members 30A and 30B eachhaving a small Young's modulus are chamfered (notched).

In the optical fiber scanning apparatus 10A, a difference dFR betweenresonance frequencies is larger than the difference dFR between thereference frequencies in the optical fiber scanning apparatus 10. Thisis presumed to be because an influence of the fixing members 30A and 30Brespectively embedded in the grooves T20A and T20B the corner portionsof which are chamfered on vibration of the optical fiber 12 is largerthan an influence of the fixing members 30C and 30D respectivelyembedded in grooves T20C and T20D corner portions of which are notchamfered.

The optical fiber scanning apparatus 10A can perform more stablescanning because the difference dFR between the resonance frequencies islarger than the difference dFR between the resonance frequencies in theoptical fiber scanning apparatus 10.

Note that a width W, a depth D, and a length S of the groove T20 aredesigned depending on a specification. For example, if an outer diameterof the optical fiber 12 is 125 μm, and a length (vibration length) Lfrom a fixed end 12F2 to a free end 12F1 is 10 mm, the width W is 80 μmto 125 μm, and the depth D is 150 μm to 300 μm.

Modification 2 to First Embodiment

A width W of a groove T20 in a shape of the groove T20 exerts a largestinfluence on a resonance frequency FR.

In a ferrule 20B in an optical fiber scanning apparatus 10B according toa modification 2 illustrated in FIG. 8, the width W of the groove T20 islarge, and an entire periphery of an optical fiber 12 is covered withfirst fixing members 30A and 30B and second fixing members 30C and 30Dwhich are embedded in the groove T20. In the optical fiber scanningapparatus 10B, the width W of the groove T20 is large. Thus, a resonancefrequency FR can be more efficiently changed.

Further, in the ferrule 20B, grooves T20A and T20B in a Y-axis directioneach have a small length S. In other words, the groove T20 may not reacha side surface 20SS of the ferrule. However, two grooves T20C and T20Dwhich reach the side surface 20SS of the ferrule can be simultaneouslyformed using a dicing saw or the like. Accordingly, the groove T20extending to the side surface 20SS of the ferrule, that is, the grooveT20 having an opening on the side surface 20SS of the ferrule ispreferable.

Modification 3 to First Embodiment

In an optical fiber scanning apparatus 10C according to a modification 3illustrated in FIG. 9, a groove T20C is a donut-shaped recess portionformed over an entire outer periphery of a through hole H20. In otherwords, a diameter of the through hole H20 on a distal end surface 20SAof a ferrule 20C is apparently large.

First fixing members 30A and 30B and second fixing members 30C and 30Dare each designed to match a shape of the groove T20C and an outerdiameter of an optical fiber 12, and are combined to be embedded in thegroove T20C, to fix the optical fiber 12.

Note that although an outer periphery of the groove T20C in the opticalfiber scanning apparatus 10C is circular, the outer periphery may berectangular or polygonal.

Modification 4 to First Embodiment

In an optical fiber scanning apparatus 10D according to a modification 4illustrated in FIG. 10, an outer periphery of an optical fiber 12 isfixed by first fixing members 30A and 30B each composed of siliconeresin (a Young's modulus: 4 MPa) embedded in a pair of grooves T20A andT20B facing each other in a first direction (Y-axis direction). Theouter periphery of the optical fiber 12 is fixed by a wall surface of athrough hole H20 in a ferrule 20D composed of nickel (a Young's modulus:207 GPa) in a second direction (X-axis direction). Note that although awidth of the pair of grooves T20A and T20B may be smaller than adiameter of the through hole H20, the width W is preferablysubstantially the same as the diameter.

The optical fiber scanning apparatus 10D according to the modification 4has the same effect as the effect of the optical fiber scanningapparatus 10 because a first fixing member which fixes the optical fiber12 in the first direction and a second fixing member which fixes theoptical fiber 12 in the second direction differ in Young's modulus. Thewidth W of the grooves can be made larger. Thus, a resonance frequencyFR can be more effectively changed.

In the optical fiber scanning apparatus according to the embodiment, atleast one of a first fixing member and a second fixing member may beformed on a distal end surface and embedded in a groove having anopening on a wall surface of a through hole.

Second Embodiment

An optical fiber scanning apparatus 10E according to a second embodimentis similar to and has the same effect as the effect of the optical fiberscanning apparatus 10. Thus, components having the same functions areassigned the same reference numerals, and description of the componentsis omitted.

As illustrated in FIG. 11, in the optical fiber scanning apparatus 10E,an optical fiber 12 is fixed by a fixing member 31 disposed on a distalend surface 20SA of a ferrule 20E.

An outer periphery of the optical fiber 12 is fixed by first fixingmembers 31A and 31B composed of epoxy resin in a first direction (Y-axisdirection), and is fixed by second fixing members 31C and 31D composedof solder in a second direction (X-axis direction). Note that an outerperipheral surface of the optical fiber 12 on which the second fixingmembers 31C and 31D are disposed is coated with gold which can besolder-bonded.

The optical fiber scanning apparatus 10E is easily manufactured becausea groove to be embedded with a fixing member needs not be formed in theferrule 20.

Note that in the foregoing description, the optical fiber scanningapparatus 10 using the piezoelectric driving method in which the drivingsection includes the piezoelectric elements 25, for example, has beendescribed. However, the optical fiber scanning apparatus according tothe embodiment may use an electromagnetic driving method in which thedriving section includes a magnet. In the electromagnetic drivingmethod, an alternating current magnetic field is applied from outside toan optical fiber to which a magnetic body (magnet) is attached. In theoptical fiber scanning apparatus using the electromagnetic drivingmethod, a holding section (ferrule) may be not a rectangularparallelepiped but a circular column or a polygonal column having apolygon with five or more sides and angles as its base.

Although the Lissajous scanning has been mainly described as thescanning method, when resonance frequencies in an X-axis direction and aY-axis direction are also made to differ in the spiral scanning or theraster scanning, an unexpected trajectory does not easily occur inrespective vibrations in the axis directions so that a trajectory havinglittle distortion can be obtained.

In the above-described optical fiber scanning apparatus 10, for example,the first fixing member and the second fixing member are the same inshape, particularly the same in a shape of an abutment surface abuttingon an optical fiber, and are the same in area. However, the first fixingmember and the second fixing member may respectively have differentshapes.

Note that it goes without saying that an endoscope including any one ofthe optical fiber scanning apparatuses 10A to 10D according to themodifications to the first embodiment or the optical fiber scanningapparatus 10E according to the second embodiment has an effect of theendoscope 9 according to the first embodiment, and further has an effectof the optical fiber scanning apparatus included in the endoscope.

The present invention is not limited to each of the above-describedembodiments and modifications, but various changes, combinations, andapplications are possible without departing from the scope and spirit ofthe invention.

What is claimed is:
 1. An optical fiber scanning apparatus comprising:an optical fiber configured to emit illumination light from a free endof the optical fiber, the free end being configured to move according toa vibration of the optical fiber; a drive apparatus configured tovibrate the free end of the optical fiber in a first direction and in asecond direction perpendicular to the first direction; a ferrulecomprising: a through hole through which the optical fiber is inserted,the through hole being extended in an optical axis direction; a pair offirst grooves formed on a distal end surface of the ferrule in the firstdirection, each of the pair of first grooves including an opening on awall surface of the through hole; and a pair of second grooves formed onthe distal end surface of the ferrule in the second direction, each ofthe pair of second grooves including the opening on a wall surface ofthe through hole; a pair of first fixing members respectively embeddedin the pair of first grooves to fix the optical fiber with respect tothe first direction; and a pair of second fixing members respectivelyembedded in the pair of second grooves to fix the optical fiber withrespect to the second direction.
 2. The optical fiber scanning apparatusaccording to claim 1, wherein the pair of first fixing members and thepair of second fixing members are composed of different materials,respectively.
 3. The optical fiber scanning apparatus according to claim1, wherein: the pair of first fixing members are composed of a firstmaterial having a first Young's modulus, the pair of second fixingmembers are composed of a second material having a second Young'smodulus, and the first Young's modulus is smaller than the secondYoung's modulus.
 4. The optical fiber scanning apparatus according toclaim 1, wherein at least one of the pair of first fixing members and atleast one of the pair of second fixing members is composed of resin. 5.The optical fiber scanning apparatus according to claim 1, wherein atleast one of the pair of first fixing members and at least one of thepair of second fixing members is composed of metal.
 6. The optical fiberscanning apparatus according to claim 1, wherein among corner portionsrespectively formed between the distal end surface and side surfaces ofthe ferrule, the corner portions in a direction in which the pair offirst fixing members is disposed are chamfered.